Abstract
Oil exploration and production activities are common in the northern Gulf of Mexico as well as many other coastal and near coastal areas worldwide. Seasonal hypoxia is also a common feature in the Northern Gulf, and many other coastal areas, which is likely to increase in severity and extent with continuing anthropogenic nutrient inputs. Hypoxia has well established physiological effects on many organisms, and it has been shown to enhance the toxicity of polycyclic aromatic hydrocarbons (persistent components of petroleum) in fish. The goal of this study was to examine the combined effects of hypoxia and exposure to contaminants associated with oil spills. We evaluated the effects of short term (48 hr) exposures to Corexit EC9500A, water accommodated fractions (WAF), and chemically enhanced water accommodated fractions (CEWAF) prepared from Southern Louisiana Sweet Crude Oil (MC 242) on survival of sheepshead minnow (Cyprinodon variegatus) larvae held under normoxic (ambient air) or hypoxic (2 mg/L O2) conditions. Results demonstrated that hypoxia significantly enhances mortality observed in response to Corexit or CEWAF solutions. In the latter case, significant interactions between the two stressors were also observed. Our data supports the need to further evaluate the combined stresses imparted by hypoxia and exposure to petroleum hydrocarbons and dispersants.
Highlights
The 2010 Deepwater Horizon oil spill in the Gulf of Mexico was the largest accidental release of petroleum in U.S waters
The objective of our study was to examine the influence of hypoxia on contaminants associated with oil spills in coastal waters, evaluating survival in sheepshead minnow larvae after short term exposures to a commonly used oil spill dispersant, Corexit EC9500A, as well as water accommodated fractions (WAF) and chemically enhanced water accommodated fractions (CEWAF) solutions made from Southern Louisiana Sweet Crude Oil (MC-242) under normoxic and hypoxic conditions
Our studies show that hypoxia as a co-stressor significantly decreased survival of 1 dph sheepshead minnow larvae exposed to Corexit and CEWAFs, but not WAFs
Summary
The 2010 Deepwater Horizon oil spill in the Gulf of Mexico was the largest accidental release of petroleum in U.S waters. Over 1.7 million gallons of oil were released, resulting in a large surface slick as well as a subsurface plume. Over 1.84 million gallons of dispersants were released at the surface and at depth in an attempt to mitigate the oil spill’s impact. The expansion of seasonal hypoxia is likely to provide another form of stress to organisms living in contaminated areas, in the Gulf of Mexico and in other coastal areas worldwide [4]. There is ample evidence of potential mechanisms by which co-exposure to hypoxia and oil could exacerbate the effects of their stressor alone, the combined effects of these stressors are not yet well appreciated [5]
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